#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>



int main()
{
	int grade;
	scanf("%d", &grade);
	if (grade >= 90) printf("A\n");
	else if (grade >= 80) printf("B\n");
	else if (grade >= 70) printf("C\n");
	else if (grade >= 60) printf("D\n");
	else printf("E");
	return 0;
}